took a seat.
At the table next to him were some men from the crime prevention section. He knew them by face, but not well enough to strike up a conversation. Among them were two men who were not in the police department, members of a crime prevention association. They were engaged in a lively discussion.
“These days many houses are equipped with burglar alarms,” one of the men from the crime prevention association was saying. “I think public relations by the police have had quite an effect in that area.”
Imanishi alternately ate a bite of cake and drank a sip of coffee.
“Alarms might be enough to dissuade burglars, but what hasn’t declined is the number of door-to-door peddlers,” a detective in the crime prevention section put in. “This is a real problem for us. You may avoid trouble by buying something for a hundred yen, but it is ridiculous to buy something knowing that it’s worthless.”
“Some housewives become frightened and hand over money to the peddler right away. Then the peddler becomes more obnoxious and pushes more items onto the poor victims. If they were to go ask for help from a neighbor, the peddler might steal something while they’re gone, and if the neighbors hear that it’s a gangster- peddler, they’re not likely to come to help out. It’s really a serious problem.”
“These days, though,” one of the crime prevention association members said with a chuckle, “there’s a miracle cure to get rid of pushy peddlers.”
“Really? What is that?”
“You have to install a special device.”
Imanishi overheard this comment and turned to look at the speaker. His ears had perked up when he had heard the word “peddler” in their conversation. Now that the talk was about equipment to repel peddlers, his attention was drawn even more.
“It’s like this…” the man from the association explained. “First I’ll tell you the effect. The peddler starts to feel sick and scurries away.”
“Really? Is that true?”
“It’s true,” the speaker nodded.
“Well, that really is a miracle cure. It’s funny to think that those pushy gangster-peddlers would run away feeling sick. What sort of equipment is it?”
Imanishi became even more curious. Drinking his coffee, Imanishi concentrated on listening.
“The machine is called an ultrasonic peddler repellent,” the man said.
“Ultrasonic…? Oh, yes, it must be a piece of electrical equipment.”
“No, it’s not electricity that causes this effect. A high sound can make the person feel sick.”
“If it’s a high sound, then wouldn’t the neighbors hear it?”
“No, it’s not that kind of high sound. I don’t understand the theory myself, but instead of causing a noise, it echoes in your body directly, making you feel strange.”
Imanishi remembered the fragment of a boring newspaper article. He had put it aside. The word “ultrasonic” had appeared in it. It was a strong force. It could drill metal, he recalled. He was intrigued. He waited until the group stood up, then he grabbed one of the detectives he knew by sight and whispered to him, “Who is that person who was talking about the peddler repellent machine just now?”
The detective told him, “That’s Yasuhiro-
“Could you introduce me to him? I’d like to ask him something.”
“Sure, glad to.”
“This is my name.” Imanishi gave Yasuhiro his card. “Thank you so much for your cooperation.” He bowed.
“Please don’t mention it.” The man named Yasuhiro also gave Imanishi his card, and the information he sought.
Imanishi left headquarters just after four o’clock. He had not felt so impatient about reaching a destination for a long time. Normally, he would have taken trains and buses, but today he made the extravagant choice of taking a taxi.
The communications research center was located in an empty lot surrounded by a flimsy wire fence. On the roof of the white, two-story, Western-style building were a parabola antenna shaped like a bowl and some steel towers for wireless transmission.
Hamanaka, the researcher Imanishi had come to see, had given instructions for a security guard to escort him to the sitting room. Soon the door opened and a man of about thirty-five with thinning hair above a broad forehead appeared.
“My name is Hamanaka.”
They exchanged name cards. On Hamanaka’s card was the designation “Post and Telecommunications Specialist.”
“I’m with the government, on temporary loan to this research center,” Hamanaka explained.
“As I mentioned to you over the telephone, I heard about the electronic peddler repellent device from a member of the crime prevention association. I hear that you invented it?”
“No, it’s not really my invention.” Specialist Hamanaka squinted his large eyes and chuckled. “The theory is very simple. But I may have been the first one to assemble it into something for practical use.”
“Could you please explain that theory to me in a way that a layman can understand?” Imanishi asked.
Hamanaka continued to smile. “It’s actually a sound.”
“A sound?”
“Yes. If I can explain a bit. We live every day among many sounds.” Hamanaka spoke, searching for simple words. “These sounds can be like notes of music, or they can be just noise. Among those sounds, there are some that are very unpleasant. For example, the sound of a saw screeching as it goes through wood, or the kind that makes you grind your teeth, like fingernails on a glass window. Those are unpleasant sounds, aren’t they?”
“They certainly are.”
“The difference in tone causes them to sound unpleasant. These tones come to us as waves through the air, so we call them sound waves. If these sound waves are sent in cycles at certain frequencies they can be very unpleasant for human beings. The peddler repellent device utilizes this acoustic effect.”
“I see.” Realizing that the theoretical discussion would become complicated from here on, Imanishi waited for the next words.
“If I can give you an example,” Hamanaka continued, smiling, “let’s say that you were made to listen to a low- frequency sound of ten cycles for several minutes. In this case, the sound is not what we normally call sound, but might be better described as vibrations. So it might be considered that you are not listening to the sound but are feeling the sound.”
Imanishi looked confused, so Hamanaka’s explanation became even more basic.
“You would feel uncomfortable after hearing that vibration for a while. Your head would start aching, and your body might start shaking. It’s a strange phenomenon.”
“Does one really react that way?” Imanishi asked, leaning forward.
“Yes, most definitely. What I just explained was a low sound that may just barely be heard or not heard at all. The same can be said about high sounds.”
“High sounds?”
“Yes. High sounds over ten thousand cycles in frequency. If one is exposed to twenty-thousand- to thirty- thousand-cycle sounds, rather than hearing them, one starts to feel strange. Both high-frequency and low-frequency sound waves are felt as very unpleasant sensations.”
He continued, “Please look at this. This diagram plots the average range of auditory senses of a number of people in terms of frequency and volume. The numbers along the bottom are the frequencies, and the numbers on the left side are the levels of volume. On the right side is sound pressure. The range of audible frequencies is usually said to be from ten thousand to twenty thousand cycles. As this diagram shows, the range narrows at lower volumes. We call the curve at the bottom the minimum auditory value, or the auditory limit. This means that we cannot hear sounds below this point. The curve at the top of this diagram is called the maximum auditory value, or the sensory limit. If we hear a sound higher than this, we feel discomfort or pain, or some other sensation.”
“So,” Imanishi said, “between twenty thousand and thirty thousand cycles, sound can make you sick?”
Hamanaka nodded.
